Financing - Debt (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Unsecured Debt
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 3,300.0	$ 3,300.0
Debt, Weighted-Average Interest Rate	4.84%	4.84%
Debt Instrument, Covenant Compliance	As of June 30, 2023, Boardwalk Pipelines and its operating subsidiaries were in compliance with their debt covenants.
Line of Credit
Line of Credit Facility [Abstract]
Line of Credit Facility, Remaining Borrowing Capacity	$ 1,000.0	$ 1,000.0
Line of Credit Facility, Covenant Compliance	The Company and its subsidiaries were in compliance with all covenant requirements under its revolving credit facility as of June 30, 2023.
Line of Credit | Amendment No. 3 Credit Agreement - 2021
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,000.0
Line of Credit Facility, Expiration Date	May 27, 2027
Line of Credit | Amendment No. 5 Credit Agreement - 2023
Line of Credit Facility [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	$ 912.2
Line of Credit Facility, Expiration Date	May 26, 2028
Maturity date extension term	2 years